A proposal for the continuing investigation of the technique known as computerized transaxial tomography (CAT or CT) to nuclear medical imaging to yield three-dimensional, quantitatively accurate images of the spatial distribution of radionuclides within living subjects. We and others have demonstrated that a wide variety of techniques for CAT can be applied to emission (i.e. radionuclide) tomography. Developmental research in our laboratory has produced a highly functional emission transaxial tomographic system based upon a standard Anger gamma camera. The primary aims of this continuing research are to extend the performance and versatility of this system and investigate the clinical utility of emission CAT. Specific objectives include the development of improved collimator designs, development and implementation of computer algorithms to permit the use of converging and diverging collimators, to improve and implement techniques for attenuation correction and to develop scanning techniques for imaging a number of specific organs including brain, heart. liver and adrenals.